The present invention relates to a turbo-compressor and a method for controlling a capacity thereof, and in particular, relates to a turbo-compressor being controllable on the capacity with using variable inlet guide vanes and the capacity control method thereof.
With the turbo-compressor relating to the conventional art, for the purpose of protecting it from surging occurring in a region of low flow rate, it is common to shift the turbo-compressor from a loaded operation to an unloaded operation, by fully closing inlet guide vanes provided in a suction side while a blow-off valve provided in a discharge side fully opened. Thus in this method, the characteristic of the compressor is shifted into an outside of the region where the surging occurs, in a suction flow rate with respect to discharge pressure thereof, by bringing the discharge pressure to be equal to the atmospheric pressure.
With such the method for avoiding from the surging as was mentioned above, it is possible to avoid the surging, however the power consumption of the compressor cannot be reduced so much. Then, a method for reducing the power consumption of the compressor is described, for example, in Japanese Patent Laying-Open No. Hei 4-136498 (1990). With the capacity control method described in this publication, a receiver tank is provided, so as to be used as a buffer for pressure fluctuation, and it is described that a setting value of pressure within the receiver tank is increased up to an upper limit allowable when a consumption gas amount comes down, thereby reducing a time-period of the unloaded operation. In this instance, when the pressure fluctuation within the receiver tank is frequent, the operation of the inlet guide vanes is lessened, thereby to prevent it from hunching.
Another example of the capacity control method of the compressor is described, for example, in Japanese Patent Laying-Open No. Hei 1-167498 (1989), adopting a low pressure control, as well as, an alternating control between a loaded operation and an unloaded operation. In this publication, the setting value of the discharge pressure is increased when consumption gas amount is lessened, in the same manner as was described in the Japanese Patent Laying-Open No. Hei 4-136498 (1990) mentioned above.
An object is, according to the present invention, to provide a turbo-compressor controllable in capacity thereof, being improved in reliability. Other object is, according to the present invention, to provide a turbo-compressor being able to elongate a cycle time for maintenance. Further other object is, according to the present invention, to provide a turbo-compressor, in which inlet guide vanes can be made long in lifetime thereof. Then, at least any one of those objects can be achieved, according to the present invention.
For accomplishing the object(s) mentioned above, according to the present invention, there is provided a turbo-compressor, comprising: a compressor main body for compressing an operation fluid therein; an inlet guide vane apparatus being provided on a suction side of said compressor main body and having a plural number of guide vanes therein; a blow-off valve being provided on a discharge side of said compressor main body and being variable in opening thereof; a pressure detector means for detecting discharge pressure of said compressor; memory means for memorizing at least any one of a time-period and a number of times of operations of said inlet guide vane apparatus, when being operated by a guide vane opening being equal or less than a setting limit thereof; and a controller apparatus for controlling said blow-off valve and said guide vanes upon basis of values memorized in said memory means.
According to the present invention, preferably, there is provided the turbo-compressor, as described in the above, wherein said controller apparatus shifts the compressor main body into a unloaded operation condition where the opening of said guide vanes is fully closed, if pressure detected by said pressure sensor comes up to be equal or greater than a preset pressure in a case where the time-period or the number of times of operations of the compressor main body is equal or less than a predetermined value, while setting said guide vanes to be equal or less than a setting limit in the opening thereof, and also there is provided the turbo-compressor, preferably, as described in the above, wherein said controller apparatus controls said blow-off valve on the opening thereof while setting the opening of said guide vanes at a setting limit opening thereof, when pressure detected by said pressure sensor comes up to be equal or greater than a preset pressure at the time-period or the number of times of operations of the compressor main body comes up to be equal or less than a predetermined value, while setting said guide vanes to be equal or less than a limit in the opening thereof.
As other invention, for accomplishing the object(s) mentioned above, there is provided a capacity control method of a turbo-compressor with using an inlet guide vane apparatus and a blow-off valve, comprising the following steps of: opening said blow-off valve while bringing a guide vane opening of said guide vane apparatus into full-closed condition, when a time-period or a number of times of operations of the compressor is equal or less than a predetermined value, under condition of flow rate being equal or less than a surging limit flow rate, in an operation at a flow rate being equal or less than the surging limit of said compressor; and controlling said blow-off valve in opening thereof based upon a discharge pressure of said turbo-compressor, while setting opening of guide vanes of said inlet guide vane apparatus at a setting limit value, when the time-period or the number of times of operations exceeds a predetermined value in frequency thereof.
Preferably, there is provided the capacity control method of a turbo-compressor, as described in the above, wherein the guide vanes of said inlet guide vane apparatus are fully opened in the opening thereof, when the discharge pressure comes down to be equal or less than a second preset pressure, in an operation of controlling said blow-off valve while setting the guide vanes of said inlet guide vane apparatus at the setting limit value.
Further other invention, for accomplishing the object(s) mentioned above, there is also provided a capacity control method of a turbo-compressor, for driving by shifting among an unloaded operation to a loaded operation and a constant pressure control, comprising the following steps of: bringing the turbo-compressor into the unloaded operation, when a time-period or a number of times of operations of the compressor is equal or less than a predetermined value in frequency thereof, under condition of flow rate being equal or less than a surging limit flow rate, in an operation at flow rate being equal or less than the surging limit of said compressor; and bringing the turbo-compressor into the constant pressure operation, with using said blow-off valve, when the time-period or the number of times exceeds the predetermined value.
More preferably, the capacity control method of a turbo-compressor, as described in the above: wherein the turbo-compressor is changed into the unloaded operation when the discharge pressure comes down to be equal or less than a second setting pressure; the turbo-compressor is changed into the unloaded operation when suction flow rate of said turbo-compressor comes down to be equal or less than the predetermined value, under the constant pressure cooperation with using said blow-off valve; the setting value of frequency of the time-period or the number of times of operations is determined upon basis of a maintenance period of said turbo-compressor; or said setting value of frequency is obtained through dividing an operation time-period of the blow-off valve per a week by an operation time-period of the unloaded operation per one (1) time thereof.